1. Field of the Invention
This invention relates to an air compressor, particularly to one composed of a machine base, a transmission device, a cylinder, a valve body, an automatic pressure-releasing valve and a manual pressure-releasing valve. The transmission gear of the transmission device is driven by a motor to rotate and actuate a subordinate gear to rotate together with a cam, which, by its eccentric acceleration of gravity, makes a connecting rod and a piston move up and down repeatedly in the cylinder. When the piston rod together with the piston is moved downward, air will get into the cylinder through the air hole of the piston; when the piston is moved upward, air in the cylinder will be compressed to get into the valve body, and then exhaust out of the valve body through an air outlet and be guided by an air duct to be pumped into the tyre, thus the pressure of the exhausted air being very steady. Besides, when the pressure gauge of the air compressor indicates that the air pressure is excessive, surplus pressure can be released by the automatic pressure-releasing valve or by the manual pressure-releasing valve so as to protect the components inside the air compressor from damaged and ensure safety of a tire receiving compressed air from the air compressor.
2. Description of the Prior Art
A conventional air compressor, as shown in FIGS. 1 and 2, includes a motor 10 assembled on a fixing base 11 in the front. A transmission gear 12 is fixed on the shaft of the motor 10, and a subordinate gear 13 is provided on the fixing base 11 and meshed with the transmission gear 12. The subordinate gear 13 has an eccentric shaft 14 connected with a piston rod 15, which has its upper end assembled with a piston 16 positioned in a cylinder 17. The cylinder 17 is secured on the upper portion of the fixing base 11, having an intake valve 18 and an exhaust valve 19. The motor 10 is started to drive the transmission gear 12 to rotate together with the subordinate gear 13, and synchronously the eccentric shaft 14 of the subordinate gear 13 actuates the connecting rod 15 and the piston 16 to move up and down in the cylinder 17. When the piston 16 is moved downward, external air will be sucked into the cylinder 17 through the intake valve 18, but when the piston 16 is moved upward, air in the cylinder 17 will be compressed to get out of the exhaust valve 19.
However, the subordinate gear 13 of the conventional air compressor is directly rotated by the transmission gear 12, therefore the moving distance of the piston rod 15 is comparatively short and consequently its driving force is comparatively small, unable to suck in and exhaust out a large quantity of air. Besides, the conventional air compressor provides with no manual pressure-releasing valve to release surplus pressure from the interior of the compressor, possible to damage the components inside the compressor.
The objective of the invention is to offer an air compressor provided with an automatic pressure-releasing valve and a manual pressure-releasing valve, able to automatically or manually release surplus pressure from the interior of the compressor to ensure safety of a tyre.
The air compressor in the present invention includes a machine base having a chamber formed inside and a through opening bored in the topside and communicating with the chamber, the machine base is further provided in one side with a vertical opening defined by two opposite side walls respectively bored with a shaft hole having a recess formed outside for receiving a bearing, with a through hole bored above the cut groove, the machine base fixed thereon with a motor seat having a shaft hole. The air compressor also has a transmission device composed of a motor, a transmission gear, a subordinate gear, a cam, an eccentric shaft, a piston rod, a piston, a covering member, a piston air ring and a gasket. The motor is assembled on the motor seat of the machine base, with the transmission gear secured on the shaft of the motor and positioned in the through hole of the machine base. The subordinate gear is inserted by a transmission shaft and positioned in the cut groove of the machine base to mesh with the transmission gear. The cam is fitted on one end of the transmission shaft and having a shaft hole in the center, and an insert hole bored under the shaft hole and fixed therein with an eccentric shaft. The piston rod is provided with an accommodating hole at the bottom for receiving a bearing, which is secured on the eccentric shaft, the piston assembled on the upper end of the connecting rod and having an air hole in the center, with the cover fastened on the piston and having a C-shaped hole formed therebetween with a openable stop sheet for covering the air hole of the piston. The gasket is fitted in the piston air ring and together disposed on the piston, and a cylinder is fixedly assembled on the machine base and having an air hole in the topside, with a valve combined on the cylinder and having a vertical air passage passing through its bottom side, and a lower side provided with a connecter for connecting a pressure gauge and the other lower side provided with an automatic pressure-releasing holder and an air outlet. The valve is further provided with a manual pressure-releasing holder at an upper portion, with an automatic pressure-releasing valve fitted in the automatic pressure-releasing holder of the valve body and composed of a stuffing member, a spring and a regulating member. A manual pressure-releasing valve is fitted in the manual pressure-releasing holder of the valve body and composed of a stuffing member, a spring, a push needle and a fixing cap.